钻井罐顶气组分地球化学特征及其在储层辨识中的应用

Geochemical feature of head-space gas components of drill well and its application to petroleum reservoir identification

罐顶气分析可以快速对钻井油气层深度进行识别,其气态烃参数也经常用于判别储层油气属性。由于钻井罐顶气取样过程造成的不可避免的气体损失,罐顶气气态烃性质能否代表储层天然气的气体属性存在一定的争论。因此,利用罐顶气气态烃参数识别储层油气属性也就存在一定的不确定性。通过对某钻井储层天然气和同等深度罐顶气的对比研究,建立了罐顶气分析判别储层油气属性模型。结果表明,储层天然气中气态烃(C1-C5)含量与同等深度的罐顶气气态烃含量存在一定的差异,导致利用罐顶气气态烃含量指标参数判识的储层油气藏属性与利用储层天然气判识的油气藏实际属性亦存在一定差别;而罐顶气气态烃的碳、氢同位素比值与储层天然气的碳、氢同位素比值一致。因此,钻井录井中,罐顶气气态烃含量仅能用来识别钻井油气层的深度,其碳、氢同位素比值可用来判别储层油气属性。

Head?space gas of well logging is a fast and cheap technique to identify the depth of oil and gas reservoir, and the hydrocar?bon indexes are usually used to distinguish the characteristics of oil or gas in the reservoir. Due to the unavoidable weight loss of gas during the sampling process of head?space gas, the problem as to whether the property of the hydrocarbons in the can is the same as the reservoir gas is an argumentative issue. Therefore, it is questionable to use the indexes of hydrocarbon of head?space gas to distinguish the characteristics of reservoir petroleum. In this study, a model for identifying characteristics of the reservoir gas or oil by head?space gas of drill core was established by a comparative study between the drill core head?space gas and the reservoir gas from the same depth. The result shows that the drill core head?space hydrocarbons are different from the reservoir hydrocarbons in concentrations, which fur?ther results in the difference of hydrocarbon indexes of the two gases in identifying the characteristics of petroleum reservoir. However, the isotopic composition (δ13 C,δD) of the hydrocarbons of the head?space gas and that of the reservoir gas are identical, suggesting that the δ13 C and δD values could be used to identify the characteristics of petroleum reservoir.